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Description

Issue summary: Writing large, newline-free data into a BIO chain using the line-buffering filter where the next BIO performs short writes can trigger a heap-based out-of-bounds write. Impact summary: This out-of-bounds write can cause memory corruption which typically results in a crash, leading to Denial of Service for an application. The line-buffering BIO filter (BIO_f_linebuffer) is not used by default in TLS/SSL data paths. In OpenSSL command-line applications, it is typically only pushed onto stdout/stderr on VMS systems. Third-party applications that explicitly use this filter with a BIO chain that can short-write and that write large, newline-free data influenced by an attacker would be affected. However, the circumstances where this could happen are unlikely to be under attacker control, and BIO_f_linebuffer is unlikely to be handling non-curated data controlled by an attacker. For that reason the issue was assessed as Low severity. The FIPS modules in 3.6, 3.5, 3.4, 3.3 and 3.0 are not affected by this issue, as the BIO implementation is outside the OpenSSL FIPS module boundary. OpenSSL 3.6, 3.5, 3.4, 3.3, 3.0, 1.1.1 and 1.0.2 are vulnerable to this issue.

PUBLISHED Reserved 2025-12-16 | Published 2026-01-27 | Updated 2026-01-29 | Assigner openssl

Problem types

CWE-787 Out-of-bounds Write

Product status

Default status
unaffected

3.6.0 (semver) before 3.6.1
affected

3.5.0 (semver) before 3.5.5
affected

3.4.0 (semver) before 3.4.4
affected

3.3.0 (semver) before 3.3.6
affected

3.0.0 (semver) before 3.0.19
affected

1.1.1 (custom) before 1.1.1ze
affected

1.0.2 (custom) before 1.0.2zn
affected

Credits

Petr Šimeček (Aisle Research) reporter

Stanislav Fort (Aisle Research) reporter

Stanislav Fort (Aisle Research) remediation developer

Neil Horman remediation developer

References

openssl-library.org/news/secadv/20260127.txt (OpenSSL Advisory) vendor-advisory

github.com/...ommit/4c96fbba618e1940f038012506ee9e21d32ee12c (3.6.1 git commit) patch

github.com/...ommit/6845c3b6460a98b1ec4e463baa2ea1a63a32d7c0 (3.5.5 git commit) patch

github.com/...ommit/68a7cd2e2816c3a02f4d45a2ce43fc04fac97096 (3.4.4 git commit) patch

github.com/...ommit/384011202af92605d926fafe4a0bcd6b65d162ad (3.3.6 git commit) patch

github.com/...ommit/475c466ef2fbd8fc1df6fae1c3eed9c813fc8ff6 (3.0.19 git commit) patch

cve.org (CVE-2025-68160)

nvd.nist.gov (CVE-2025-68160)

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