CVE-2024-0853Network attack vector

Server authentication bypass via cached TLS session

Published Feb 3, 2024 · Updated Jun 20, 2025

Improper certificate revocation checking in curl 8.5.0 allows remote attackers to bypass OCSP verification during TLS session reuse. The OpenSSL backend retains a session ID after verifystatus fails, so a later connection to the same hostname reuses that session and skips the status check. Reachability requires an OpenSSL build, TLS 1.2, OCSP status verification, and a fresh cached session; the client can then accept a server whose revocation check failed.

CVSS severity5.3
Medium
EPSS probability1.10%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Improper certificate revocation checking in curl 8.5.0 allows remote attackers to bypass OCSP verification during TLS session reuse. The OpenSSL backend retains a session ID after verifystatus fails, so a later connection to the same hostname reuses that session and skips the status check. Reachability requires an OpenSSL build, TLS 1.2, OCSP status verification, and a fresh cached session; the client can then accept a server whose revocation check failed.

The record

CVE
CVE-2024-0853
Published
Feb 3, 2024
Updated
Jun 20, 2025
Vendor
curl
Product
curl
Classifications
CWE-295, CWE-299, T1557
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Feb 3, 2024CVE publishedPublication date reported by the CVE source.
  2. Jun 20, 2025Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=8.5.0 <=8.5.0

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

curl · curlversion=8.5.0 <=8.5.0

Published CVSS scores

5.3CISA-ADPCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N
5.3NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-295Improper Certificate Validation
CWE-299Improper Check for Certificate Revocation
T1557Adversary-in-the-Middle

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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