CVE-2020-25685
A flaw was found in dnsmasq before version 2.83. When getting a reply from a forwarded query, dnsmasq checks in forward.c:reply_query(),…
- Published
- Updated
- Reserved
- Assigned by
- redhat
Description
A flaw was found in dnsmasq before version 2.83. When getting a reply from a forwarded query, dnsmasq checks in forward.c:reply_query(), which is the forwarded query that matches the reply, by only using a weak hash of the query name. Due to the weak hash (CRC32 when dnsmasq is compiled without DNSSEC, SHA-1 when it is) this flaw allows an off-path attacker to find several different domains all having the same hash, substantially reducing the number of attempts they would have to perform to forge a reply and get it accepted by dnsmasq. This is in contrast with RFC5452, which specifies that the query name is one of the attributes of a query that must be used to match a reply. This flaw could be abused to perform a DNS Cache Poisoning attack. If chained with CVE-2020-25684 the attack complexity of a successful attack is reduced. The highest threat from this vulnerability is to data integrity.
Timeline
ID reserved
By redhat
- 4 months later
· 4 months later
Published
- 5 years later
· 5 years later
Record updated
Changes after publication (a new score, a public exploit, EPSS crossing 1, 10 or 50 %, leaving KEV) are kept since November 2026; earlier ones are not known.
Scores
| Scored by | CVSS | Score | Vector |
|---|---|---|---|
| NVDNVD · Modified | 3.1 | Low3.7 | CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:N |
- EPSS (exploitation in 30 days)
- 2.2% · top 17% of all CVEs (7 Nov 2026)
The list uses the assigner's score when there is one, then CISA's, then NVD's: Low 3.7.
Weakness
Affected products
dnsmasq
- affected dnsmasq 2.83
References (8)
- https://www.jsof-tech.com/disclosures/dnspooq/ (opens in a new tab)x_transferred
- https://bugzilla.redhat.com/show_bug.cgi?id=1889688 (opens in a new tab)x_transferred
- FEDORA-2021-84440e87ba (opens in a new tab)vendor-advisoryx_transferred
- GLSA-202101-17 (opens in a new tab)vendor-advisoryx_transferred
- DSA-4844 (opens in a new tab)vendor-advisoryx_transferred
- FEDORA-2021-2e4c3d5a9d (opens in a new tab)vendor-advisoryx_transferred
- https://www.arista.com/en/support/advisories-notices/security-advisories/12135-security-advisory-61 (opens in a new tab)x_transferred
- https://www.kb.cert.org/vuls/id/434904 (opens in a new tab)
Sources
The same CVE in the primary databases and aggregators, to check against.
- CVE.org record (opens in a new tab)
- CVE List JSON (GitHub) (opens in a new tab)
- NVD (opens in a new tab)
- FIRST EPSS (opens in a new tab)
- OSV.dev (opens in a new tab)
- GitHub Advisories (opens in a new tab)
- CIRCL Vulnerability-Lookup (opens in a new tab)
Badge for a README or a ticket
[](https://trackcve.app/cve/CVE-2020-25685)Record last updated .