CVE-2021-31807

CVE-2021-31807 is a medium-severity vulnerability in Squid-cache Squid with a CVSS 3.x base score of 6.5. Its EPSS exploit-prediction score of 16% places it in the 97th percentile, indicating an elevated likelihood of exploitation. The underlying weakness is classified as CWE-190.

Key facts

Description

An issue was discovered in Squid before 4.15 and 5.x before 5.0.6. An integer overflow problem allows a remote server to achieve Denial of Service when delivering responses to HTTP Range requests. The issue trigger is a header that can be expected to exist in HTTP traffic without any malicious intent.

Frequently asked questions

What is CVE-2021-31807?
An issue was discovered in Squid before 4.15 and 5.x before 5.0.6. An integer overflow problem allows a remote server to achieve Denial of Service when delivering responses to HTTP Range requests. The issue trigger is a header that can be expected to exist in HTTP traffic without any malicious intent.
How severe is CVE-2021-31807?
CVE-2021-31807 has a CVSS 3.x base score of 6.5, rated medium severity. It is exploitable over network with low attack complexity, requires low privileges and no user interaction. Impact on confidentiality is none, integrity none, and availability high.
Is CVE-2021-31807 being actively exploited?
It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 16% (97th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2021-31807?
CVE-2021-31807 primarily affects Squid-cache Squid. In total, 27 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.
How do I fix CVE-2021-31807?
Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.
When was CVE-2021-31807 published?
CVE-2021-31807 was published on 2021-06-08 and last updated on 2026-06-17.

References

Affected products (27)

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Other CWE-190 (Integer Overflow or Wraparound) vulnerabilities

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Threat intelligence

Threat-intel indicators referencing this CVE: