NULL pointer deref in signature_algorithms processing

Summary

An OpenSSL TLS server may crash if sent a maliciously crafted renegotiation ClientHello message from a client. If a TLSv1.2 renegotiation ClientHello omits the signature_algorithms extension (where it was present in the initial ClientHello), but includes a signature_algorithms_cert extension then a NULL pointer dereference will result, leading to a crash and a denial of service attack. A server is only vulnerable if it has TLSv1.2 and renegotiation enabled (which is the default configuration). OpenSSL TLS clients are not impacted by this issue. All OpenSSL 1.1.1 versions are affected by this issue. Users of these versions should upgrade to OpenSSL 1.1.1k. OpenSSL 1.0.2 is not impacted by this issue. Fixed in OpenSSL 1.1.1k (Affected 1.1.1-1.1.1j).

Timeline

1. Mar 25, 2021, 2:25 PM UTCCVE published
2. Oct 8, 2026, 9:05 PM UTCCISA SSVC assessment

   Exploitation: none · Automatable: yes · Technical impact: partial

3. Oct 8, 2026, 9:13 PM UTCRecord last updated
4. Oct 22, 2026EPSS reached 10%

   FIRST estimates at least a 10% chance of exploitation in the next 30 days

Affected versions

• OpenSSL OpenSSL

  Fixed in OpenSSL 1.1.1k (Affected 1.1.1-1.1.1j)

• nodeBitnami

  From 10.0.0 · fixed in 10.12.1; From 10.13.0 · fixed in 10.24.1; From 12.0.0 · fixed in 12.12.1; From 12.13.0 · fixed in 12.22.1; From 14.0.0 · fixed in 14.14.1; From 14.15.0 · fixed in 14.16.1; From 15.0.0 · fixed in 15.14.0

• node-minBitnami

  From 10.0.0 · fixed in 10.12.1; From 10.13.0 · fixed in 10.24.1; From 12.0.0 · fixed in 12.12.1; From 12.13.0 · fixed in 12.22.1; From 14.0.0 · fixed in 14.14.1; From 14.15.0 · fixed in 14.16.1; From 15.0.0 · fixed in 15.14.0

• openssl-srccrates.io

  fixed in 111.15.0

• openssl-srccrates.io

  From 0.0.0-0 · fixed in 111.15.0

References 25