Debian LinuxOperating system · Debian
CVE-2023-5981
Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.
NVD · uneditedA vulnerability was found that the response times to malformed ciphertexts in RSA-PSK ClientKeyExchange differ from response times of ciphertexts with correct PKCS#1 v1.5 padding.
Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.
dbcve analysis · high confidenceThis is a timing side-channel vulnerability (Bleichenbacher-style) in RSA-PSK ClientKeyExchange where server response times differ between malformed ciphertexts and those with correct PKCS#1 v1.5 padding. An attacker can exploit this timing difference to potentially recover plaintext or forge RSA signatures through iterative oracle-based attacks.
Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.
Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.
NVD · CPE data
Debian LinuxOperating system
= 10.0
LinuxOperating system
= 8.0= 9.0
FedoraOperating system
= 37= 38< 3.8.2CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.
From the vector- Attack vector
- Network
- Complexity
- High
- Privileges
- None
- User interaction
- None
- Scope
- Unchanged
- Confidentiality
- High
- Integrity
- None
- Availability
- None
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N
Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.
dbcve checksWork through these to decide whether this CVE applies to you.
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Identify GnuTLS library versionRun 'gnutls-cli --version' or check the installed package version via your system package manager (dpkg -l libgnutls* or rpm -qa | grep gnutls)Affected if The installed GnuTLS version is lower than 3.8.2
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Confirm the system runs a TLS server or client using GnuTLSIdentify whether the target system uses GnuTLS for TLS connections - check installed applications (like apache2, nginx, or custom TLS services) and their linked libraries via 'ldd <executable>' or review system documentationAffected if The system uses GnuTLS as the TLS library for services that handle RSA-PSK key exchanges
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Check if RSA-PSK cipher suites are enabled in TLS configurationReview TLS configuration files (such as /etc/gnutls/, /etc/ssl/, or application-specific TLS config) for the presence of cipher suites containing 'RSA-PSK' or 'PSK' key exchange methodsAffected if RSA-PSK or PSK cipher suites are explicitly enabled in the TLS configuration
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Identify services using RSA-PSK key exchangeExamine active TLS services and their supported cipher suites - use 'gnutls-cli -l' to list available ciphers, or scan configured services for PSK-related cipher suite listingsAffected if Any TLS service is configured to accept or advertise RSA-PSK cipher suites
A system is affected if it runs GnuTLS version below 3.8.2 AND has RSA-PSK key exchange enabled in its TLS configuration, exposing it to timing oracle attacks on RSA-PSK ClientKeyExchange.
Generated from the published advisory. Verify against your own configuration.
Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.
dbcve · scoped3.8.2
Disable RSA-PSK key exchange in TLS configurations and use forward-secret key exchanges such as ECDHE or DHE. This eliminates the oracle entirely.
GnuTLS 3.8.2 or later
- Update your system's package repository metadata
- Upgrade the GnuTLS package to version 3.8.2 or later using your distribution's package manager (e.g., 'apt update && apt install libgnutls30' for Debian, 'dnf update gnutls' for Fedora, 'yum update gnutls' for RHEL/CentOS)
- Restart any services that use GnuTLS to ensure the updated library is loaded
- Verify the installed GnuTLS version is 3.8.2 or later using 'gnutls-cli --version' or checking the installed package version
Generated from the published advisory — verify against the referenced sources before acting.
Fix this in Debian Linux
Scoped from the published advisory
- Consultation3.0 h
- Implementation4.0 h
- Testing4.0 h
- Review / QA2.0 h
An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $3,648.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2023-5981 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.
References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.
Primary sourcesPractitioner notes
ContributedPeer-ranked notes from engineers who’ve handled CVE-2023-5981 in production — separate from our analysis above.
The advisory tells you what broke. It rarely tells you what actually worked. If you’ve dealt with this one, that detail is what the next engineer is searching for.
- The version that genuinely resolved it — not the one the vendor claimed
- A config change or rule that shut the vector down
- A gotcha in the upgrade path that cost you an afternoon
No notes yet
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- Verified mitigations, workarounds, and config changes
- Version or environment caveats, and links to real fixes
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