Security Advisories

If you think you have found a security bug in Botan please contact Jack Lloyd ( If you would like to encrypt your mail please use:

pub   rsa3072/57123B60 2015-03-23
      Key fingerprint = 4E60 C735 51AF 2188 DF0A  5A62 78E9 8043 5712 3B60
      uid         Jack Lloyd <>

This key can be found in the file doc/pgpkey.txt or online at and on most PGP keyservers.


  • 2024-07-08 (CVE-2024-34702): Denial of Service Due to Excessive Name Constraints

    Checking name constraints in X.509 certificates is quadratic in the number of names and name constraints. An attacker who presented a certificate chain which contained a very large number of names in the SubjectAlternativeName, signed by a CA certificate which contained a large number of name constraints, could cause a denial of service.

    Introduced in 2.0.0, fixed in 2.19.5 and 3.5.0

    Found and reported by Bing Shi.

  • 2024-07-08 (CVE-2024-39312): Authorization Error due to Name Constraint Decoding Bug

    A bug in the parsing of name constraint extensions in X.509 certificates meant that if the extension included both permitted subtrees and excluded subtrees, only the permitted subtree would be checked. If a certificate included a name which was permitted by the permitted subtree but also excluded by excluded subtree, it would be accepted.

    Introduced in 2.0.0, fixed in 2.19.5 and 3.5.0

  • 2024-02-20: Kyber side channel

    The Kyber implementation was vulnerable to the KyberSlash1 and KyberSlash2 side channel issues.

    Introduced in 3.0.0, fixed in 3.3.0

  • 2024-02-20 (CVE-2024-34703): DoS due to oversized elliptic curve parameters

    When decoding an ASN.1 encoded elliptic curve, Botan would verify the p parameter was actually prime, and at least some minimum size. However it failed to check if the prime was far too large (for example thousands of bits), in which case checking the prime would take a significant amount of computation. Now the maximum size of arbitrary elliptic curves when decoding from ASN.1 is limited.

    Reported by Bing Shi

    Fixed in 3.3.0 and 2.19.4


  • 2022-11-16 (CVE-2022-43705): Failure to correctly check OCSP responder embedded certificate

    OCSP responses for some end entity are either signed by the issuing CA certificate of the PKI, or an OCSP responder certificate that the PKI authorized to sign responses in their name. In the latter case, the responder certificate (and its validation path certificate) may be embedded into the OCSP response and clients must verify that such certificates are indeed authorized by the CA when validating OCSP responses.

    The OCSP implementation failed to verify that an authorized responder certificate embedded in an OCSP response is authorized by the issuing CA. As a result, any valid signature by an embedded certificate passed the check and was allowed to make claims about the revocation status of certificates of any CA.

    Attackers that are in a position to spoof OCSP responses for a client could therefore render legitimate certificates of a 3rd party CA as revoked or even use a compromised (and actually revoked) certificate by spoofing an OCSP-“OK” response. E.g. an attacker could exploit this to impersonate a legitimate TLS server using a compromised certificate of that host and get around the revocation check using OCSP stapling.

    Introduced in 1.11.34, fixed in 2.19.3 and 3.0.0


  • 2020-12-21 (CVE-2021-24115): Codec encoding/decoding was not constant time

    The base64, base32, base58 and hex encoding/decoding routines used lookup tables which could leak information via a cache-based side channel attack. The encoding tables were small and unlikely to be exploitable, but the decoding tables were large enough to cause non-negligible information leakage. In particular parsing an unencrypted PEM-encoded private key within an SGX enclave could be easily attacked to leak key material.

    Identified and reported by Jan Wichelmann, Thomas Eisenbarth, Sebastian Berndt, and Florian Sieck.

    Fixed in 2.17.3

  • 2020-07-05: Failure to enforce name constraints on alternative names

    The path validation algorithm enforced name constraints on the primary DN included in the certificate but failed to do so against alternative DNs which may be included in the subject alternative name. This would allow a corrupted sub-CA which was constrained by a name constraints extension in its own certificate to issue a certificate containing a prohibited DN. Until 2.15.0, there was no API to access these alternative name DNs so it is unlikely that any application would make incorrect access control decisions on the basis of the incorrect DN. Reported by Mario Korth of Ruhr-Universität Bochum.

    Introduced in 1.11.29, fixed in 2.15.0

  • 2020-03-24: Side channel during CBC padding

    The CBC padding operations were not constant time and as a result would leak the length of the plaintext values which were being padded to an attacker running a side channel attack via shared resources such as cache or branch predictor. No information about the contents was leaked, but the length alone might be used to make inferences about the contents. This issue affects TLS CBC ciphersuites as well as CBC encryption using PKCS7 or other similar padding mechanisms. In all cases, the unpadding operations were already constant time and are not affected. Reported by Maximilian Blochberger of Universität Hamburg.

    Fixed in 2.14.0, all prior versions affected.


  • 2018-12-17 (CVE-2018-20187): Side channel during ECC key generation

    A timing side channel during ECC key generation could leak information about the high bits of the secret scalar. Such information allows an attacker to perform a brute force attack on the key somewhat more efficiently than they would otherwise. Found by Ján Jančár using ECTester.

    Introduced in 1.11.20, fixed in 2.8.0.

  • 2018-06-13 (CVE-2018-12435): ECDSA side channel

    A side channel in the ECDSA signature operation could allow a local attacker to recover the secret key. Found by Keegan Ryan of NCC Group.

    Bug introduced in 2.5.0, fixed in 2.7.0. The 1.10 branch is not affected.

  • 2018-04-10 (CVE-2018-9860): Memory overread in TLS CBC decryption

    An off by one error in TLS CBC decryption meant that for a particular malformed ciphertext, the receiver would miscompute a length field and HMAC exactly 64K bytes of data following the record buffer as if it was part of the message. This cannot be used to leak information since the MAC comparison will subsequently fail and the connection will be closed. However it might be used for denial of service. Found by OSS-Fuzz.

    Bug introduced in 1.11.32, fixed in 2.6.0

  • 2018-03-29 (CVE-2018-9127): Invalid wildcard match

    RFC 6125 wildcard matching was incorrectly implemented, so that a wildcard certificate such as b* would match any hosts *b* instead of just server names beginning with b. The host and certificate would still have to be in the same domain name. Reported by Fabian Weißberg of Rohde and Schwarz Cybersecurity.

    Bug introduced in 2.2.0, fixed in 2.5.0


  • 2017-10-02 (CVE-2017-14737): Potential side channel using cache information

    In the Montgomery exponentiation code, a table of precomputed values is used. An attacker able to analyze which cache lines were accessed (perhaps via an active attack such as Prime+Probe) could recover information about the exponent. Identified in “CacheD: Identifying Cache-Based Timing Channels in Production Software” by Wang, Wang, Liu, Zhang, and Wu (Usenix Security 2017).

    Fixed in 1.10.17 and 2.3.0, all prior versions affected.

  • 2017-07-16: Failure to fully zeroize memory before free

    The secure_allocator type attempts to zeroize memory before freeing it. Due to a error sometimes only a portion of the memory would be zeroed, because of a confusion between the number of elements vs the number of bytes that those elements use. So byte vectors would always be fully zeroed (since the two notions result in the same value), but for example with an array of 32-bit integers, only the first 1/4 of the elements would be zeroed before being deallocated. This may result in information leakage, if an attacker can access memory on the heap. Reported by Roman Pozlevich.

    Bug introduced in 1.11.10, fixed in 2.2.0

  • 2017-04-04 (CVE-2017-2801): Incorrect comparison in X.509 DN strings

    Botan’s implementation of X.509 name comparisons had a flaw which could result in an out of bound memory read while processing a specially formed DN. This could potentially be exploited for information disclosure or denial of service, or result in incorrect validation results. Found independently by Aleksandar Nikolic of Cisco Talos, and OSS-Fuzz automated fuzzing infrastructure.

    Bug introduced in 1.6.0 or earlier, fixed in 2.1.0 and 1.10.16

  • 2017-03-23 (CVE-2017-7252): Incorrect bcrypt computation

    Botan’s implementation of bcrypt password hashing scheme truncated long passwords at 56 characters, instead of at bcrypt’s standard 72 characters limit. Passwords with lengths between these two bounds could be cracked more easily than should be the case due to the final password bytes being ignored. Found and reported by Solar Designer.

    Bug introduced in 1.11.0, fixed in 2.1.0.


  • 2016-11-27 (CVE-2016-9132) Integer overflow in BER decoder

    While decoding BER length fields, an integer overflow could occur. This could occur while parsing untrusted inputs such as X.509 certificates. The overflow does not seem to lead to any obviously exploitable condition, but exploitation cannot be positively ruled out. Only 32-bit platforms are likely affected; to cause an overflow on 64-bit the parsed data would have to be many gigabytes. Bug found by Falko Strenzke, cryptosource GmbH.

    Fixed in 1.10.14 and 1.11.34, all prior versions affected.

  • 2016-10-26 (CVE-2016-8871) OAEP side channel

    A side channel in OAEP decoding could be used to distinguish RSA ciphertexts that did or did not have a leading 0 byte. For an attacker capable of precisely measuring the time taken for OAEP decoding, this could be used as an oracle allowing decryption of arbitrary RSA ciphertexts. Remote exploitation seems difficult as OAEP decoding is always paired with RSA decryption, which takes substantially more (and variable) time, and so will tend to mask the timing channel. This attack does seems well within reach of a local attacker capable of a cache or branch predictor based side channel attack. Finding, analysis, and patch by Juraj Somorovsky.

    Introduced in 1.11.29, fixed in 1.11.33

  • 2016-08-30 (CVE-2016-6878) Undefined behavior in Curve25519

    On systems without a native 128-bit integer type, the Curve25519 code invoked undefined behavior. This was known to produce incorrect results on 32-bit ARM when compiled by Clang.

    Introduced in 1.11.12, fixed in 1.11.31

  • 2016-08-30 (CVE-2016-6879) Bad result from X509_Certificate::allowed_usage

    If allowed_usage was called with more than one Key_Usage set in the enum value, the function would return true if any of the allowed usages were set, instead of if all of the allowed usages are set. This could be used to bypass an application key usage check. Credit to Daniel Neus of Rohde & Schwarz Cybersecurity for finding this issue.

    Introduced in 1.11.0, fixed in 1.11.31

  • 2016-03-17 (CVE-2016-2849): ECDSA side channel

    ECDSA (and DSA) signature algorithms perform a modular inverse on the signature nonce k. The modular inverse algorithm used had input dependent loops, and it is possible a side channel attack could recover sufficient information about the nonce to eventually recover the ECDSA secret key. Found by Sean Devlin.

    Introduced in 1.7.15, fixed in 1.10.13 and 1.11.29

  • 2016-03-17 (CVE-2016-2850): Failure to enforce TLS policy

    TLS v1.2 allows negotiating which signature algorithms and hash functions each side is willing to accept. However received signatures were not actually checked against the specified policy. This had the effect of allowing a server to use an MD5 or SHA-1 signature, even though the default policy prohibits it. The same issue affected client cert authentication.

    The TLS client also failed to verify that the ECC curve the server chose to use was one which was acceptable by the client policy.

    Introduced in 1.11.0, fixed in 1.11.29

  • 2016-02-01 (CVE-2016-2196): Overwrite in P-521 reduction

    The P-521 reduction function would overwrite zero to one word following the allocated block. This could potentially result in remote code execution or a crash. Found with AFL

    Introduced in 1.11.10, fixed in 1.11.27

  • 2016-02-01 (CVE-2016-2195): Heap overflow on invalid ECC point

    The PointGFp constructor did not check that the affine coordinate arguments were less than the prime, but then in curve multiplication assumed that both arguments if multiplied would fit into an integer twice the size of the prime.

    The bigint_mul and bigint_sqr functions received the size of the output buffer, but only used it to dispatch to a faster algorithm in cases where there was sufficient output space to call an unrolled multiplication function.

    The result is a heap overflow accessible via ECC point decoding, which accepted untrusted inputs. This is likely exploitable for remote code execution.

    On systems which use the mlock pool allocator, it would allow an attacker to overwrite memory held in secure_vector objects. After this point the write will hit the guard page at the end of the mmap’ed region so it probably could not be used for code execution directly, but would allow overwriting adjacent key material.

    Found by Alex Gaynor fuzzing with AFL

    Introduced in 1.9.18, fixed in 1.11.27 and 1.10.11

  • 2016-02-01 (CVE-2016-2194): Infinite loop in modular square root algorithm

    The ressol function implements the Tonelli-Shanks algorithm for finding square roots could be sent into a nearly infinite loop due to a misplaced conditional check. This could occur if a composite modulus is provided, as this algorithm is only defined for primes. This function is exposed to attacker controlled input via the OS2ECP function during ECC point decompression. Found by AFL

    Introduced in 1.7.15, fixed in 1.11.27 and 1.10.11


  • 2015-11-04: TLS certificate authentication bypass

    When the bugs affecting X.509 path validation were fixed in 1.11.22, a check in Credentials_Manager::verify_certificate_chain was accidentally removed which caused path validation failures not to be signaled to the TLS layer. So for affected versions, certificate authentication in TLS is bypassed. As a workaround, applications can override the call and implement the correct check. Reported by Florent Le Coz in GH #324

    Introduced in 1.11.22, fixed in 1.11.24

  • 2015-10-26 (CVE-2015-7824): Padding oracle attack on TLS

    A padding oracle attack was possible against TLS CBC ciphersuites because if a certain length check on the packet fields failed, a different alert type than one used for message authentication failure would be returned to the sender. This check triggering would leak information about the value of the padding bytes and could be used to perform iterative decryption.

    As with most such oracle attacks, the danger depends on the underlying protocol - HTTP servers are particularly vulnerable. The current analysis suggests that to exploit it an attacker would first have to guess several bytes of plaintext, but again this is quite possible in many situations including HTTP.

    Found in a review by Sirrix AG and 3curity GmbH.

    Introduced in 1.11.0, fixed in 1.11.22

  • 2015-10-26 (CVE-2015-7825): Infinite loop during certificate path validation

    When evaluating a certificate path, if a loop in the certificate chain was encountered (for instance where C1 certifies C2, which certifies C1) an infinite loop would occur eventually resulting in memory exhaustion. Found in a review by Sirrix AG and 3curity GmbH.

    Introduced in 1.11.6, fixed in 1.11.22

  • 2015-10-26 (CVE-2015-7826): Acceptance of invalid certificate names

    RFC 6125 specifies how to match a X.509v3 certificate against a DNS name for application usage.

    Otherwise valid certificates using wildcards would be accepted as matching certain hostnames that should they should not according to RFC 6125. For example a certificate issued for * should match but not or Previously Botan would accept such a certificate as also valid for

    RFC 6125 also requires that when matching a X.509 certificate against a DNS name, the CN entry is only compared if no subjectAlternativeName entry is available. Previously X509_Certificate::matches_dns_name would always check both names.

    Found in a review by Sirrix AG and 3curity GmbH.

    Introduced in 1.11.0, fixed in 1.11.22

  • 2015-10-26 (CVE-2015-7827): PKCS #1 v1.5 decoding was not constant time

    During RSA decryption, how long decoding of PKCS #1 v1.5 padding took was input dependent. If these differences could be measured by an attacker, it could be used to mount a Bleichenbacher million-message attack. PKCS #1 v1.5 decoding has been rewritten to use a sequence of operations which do not contain any input-dependent indexes or jumps. Notations for checking constant time blocks with ctgrind ( were added to PKCS #1 decoding among other areas. Found in a review by Sirrix AG and 3curity GmbH.

    Fixed in 1.11.22 and 1.10.13. Affected all previous versions.

  • 2015-08-03 (CVE-2015-5726): Crash in BER decoder

    The BER decoder would crash due to reading from offset 0 of an empty vector if it encountered a BIT STRING which did not contain any data at all. This can be used to easily crash applications reading untrusted ASN.1 data, but does not seem exploitable for code execution. Found with afl.

    Fixed in 1.11.19 and 1.10.10, affected all previous versions of 1.10 and 1.11

  • 2015-08-03 (CVE-2015-5727): Excess memory allocation in BER decoder

    The BER decoder would allocate a fairly arbitrary amount of memory in a length field, even if there was no chance the read request would succeed. This might cause the process to run out of memory or invoke the OOM killer. Found with afl.

    Fixed in 1.11.19 and 1.10.10, affected all previous versions of 1.10 and 1.11


  • 2014-04-10 (CVE-2014-9742): Insufficient randomness in Miller-Rabin primality check

    A bug in the Miller-Rabin primality test resulted in only a single random base being used instead of a sequence of such bases. This increased the probability that a non-prime would be accepted by is_prime or that a randomly generated prime might actually be composite. The probability of a random 1024 bit number being incorrectly classed as prime with a single base is around 2^-40. Reported by Jeff Marrison.

    Introduced in 1.8.3, fixed in 1.10.8 and 1.11.9