USN-8847-1: OpenSSL vulnerabilities
Ubuntu warned of OpenSSL flaws that could cause denial of service or a timing side-channel leak.
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Vulnerability4 · 3 reads
CVE-2026-35189
OpenSSL memory-growth DoS via crafted CRL distribution points
- CVSS 3.1
- 5.3 medium
- EPSS
- —
- Published
- ·
- Modified
AI analysisSummaries by Vani AI
OpenSSL grows the heap disproportionately when it caches X.509 extensions from a certificate that contains many nameRelativeToCRLIssuer CRL distribution points. A malicious peer can trigger this in a normal TLS handshake by presenting a crafted certificate, or set of certificates, that stays under the roughly 100 KiB peer-certificate size limit yet causes several hundred MiB of resident memory to be allocated. That pressure can deny service to clients, and to servers that solicit client certificates, especially when many connections allocate similarly large amounts at once. The flaw is unbounded resource allocation (CWE-770) in code outside the FIPS module boundary, so FIPS status is unaffected. No public proof of concept is known, the issue is not in CISA KEV, and CVSS has not yet been scored.
What to do: Install the OpenSSL update shipped by your operating system or vendor (Ubuntu tracks related fixes in USN-8847-1) and restart every process that links against OpenSSL so the patched library is loaded. The fix delays parsing of CRL distribution point extensions until CRL processing actually needs them, so large allocations are not held for the life of the cached certificate. Until then, watch TLS clients and servers that request client certificates for sudden resident-memory growth during handshakes, and limit concurrent handshakes where that is practical.
| Product | Affected |
|---|---|
| OpenSSL | — |
Estimated exposure
massHundreds of millions of systems plausibly ship OpenSSL; the vulnerable subset is unknown because version ranges were not provided — OpenSSL is the default TLS library on most Linux distributions and is embedded in a very large number of clients, servers, and appliances; Ubuntu notice USN-8847-1 shows distro packaging of this issue, but the source data gives no affected…
Order-of-magnitude estimate by the model from install counts, market share and public scan data it knows; verify before quoting.
Description · NVD
Issue summary: A certificate with many nameRelativeToCRLIssuer CRL distribution points causes disproportionate heap growth when OpenSSL caches X.509 extensions. Impact summary: Receiving a crafted certificate from a malicious peer can lead to significant memory pressure and possible Denial of Service in clients or in servers that solicit client certificates. CWE: CWE-770: Allocation of Resources Without Limits or Throttling Description: A certificate or a set of certificates that fits under the limit for size of certificates accepted from the peer (~100 KiB) can result in allocation of several hundred MiB of resident memory on the receiving side during a normal TLS handshake. This may be enough to crash the client or server, if multiple concurrent connections lead to similarly large memory allocations. The fix postpones processing of the CRL distribution points extensions in certificates to the time when the processed value is required for CRL processing. This avoids keeping large memory allocations for a long time when such certificates are received. FIPS impact: no The affected code is outside the FIPS module boundary.
In the news
2 storiesUSN-8847-2: OpenSSL vulnerabilities
Ubuntu USN-8847-2 backports OpenSSL fixes for a CRL denial-of-service bug and a timing side-channel to ESM 14.04-20.04 LTS.
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