Linksys E5600 Login mesh_login.cgi improper authentication
Affects Linksys E5600 running firmware v1.1.0.26. No vendor rating or fixed version is listed in the checked facts.
Written by anthropic/claude-haiku-5.5 from the sources below. Verify against them.
- Exploited
- No known exploitation
- Fix
- No fix listed
- Who is exposed
- Not reported
Do first: Workaround: The checked facts list no fix and no workaround. The flaw is in the login handler mesh_login.cgi, and the facts offer no narrower step beyond waiting for a firmware update.
- Exploitation?/40Exploitation: unknown (data gap). No CISA SSVC exploitation rating yet
- Exposure17/25No login or user action needed, reachable over the network without a login · Data gap: Advisories don't say whether default setups are affected
- Reach?/20Reach: unknown (data gap). No tracked technology or package matched
- Severity10/10CVSS 10.0
- No patch5/5No patch listed yet
What would change the score
- Would score about 77 if added to CISA KEV
- Would score about 72 if CISA's SSVC rates exploitation active
- Would score about 37 if advisories confirm default setups are exposed
CVE-2026-121615 is not in CISA's Known Exploited Vulnerabilities (KEV) catalog. No public exploit code is tracked. It is rated CVSS 10.0 (critical) and affects E5600; no fixed version is listed yet.
- Last modified
- Where the record stands: published, rejected by its publisher, or superseded by another id.What do these mean? →
- Published
- Whether CISA lists it in its Known Exploited Vulnerabilities catalog: proof that attackers are using it.What do these mean? →
- Not listed in CISA KEV
- FIRST's estimate of the chance attackers exploit it in the next 30 days, updated daily.What do these mean? →
- 0.75% · 55th percentile
- A 0-100 score for how much a CVE matters across the industry: exploitation, exposure, how widely the software is used, severity and whether a fix exists.What do these mean? →
- 32/100 · provisional
- How many real-world setups can hit the bug, from the vendor's advisory and CISA data. It does not know your setup.What do these mean? →
- Unclear
- Whether working attack code is public (Exploit-DB, Metasploit, Nuclei or GitHub). Public code makes attacks easier.What do these mean? →
- None on Exploit-DB, Metasploit or GitHub
Summary
The Linksys E5600 wireless router's login handler (its mesh_login.cgi component) can be exploited to bypass proper authentication, and the flaw can be triggered remotely. Because the vendor no longer supports this product, no fix is expected from the manufacturer.
Read the original description
A vulnerability was determined in Linksys E5600 1.1.0.26. Affected is an unknown function of the file /cgi-bin/mesh_login.cgi of the component Login Handler. Executing a manipulation can lead to improper authentication. The attack can be launched remotely. The exploit has been publicly disclosed and may be utilized. The vendor was contacted early about this disclosure but did not respond in any way. This vulnerability only affects products that are no longer supported by the maintainer.
What to do
Workaround: The checked facts list no fix and no workaround. The flaw is in the login handler mesh_login.cgi, and the facts offer no narrower step beyond waiting for a firmware update.
Timeline
- CVE published
- First seen by cve.now
- Posted on X by cve.now
Affected versions
- Linksys E5600
1.1.0.26
Evidence 6
- Advisory
- Advisory
- Advisory
- Advisory
- Exploit
- Link
Corrections
None so far.
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Questions about CVE-2026-121615
Is CVE-2026-121615 being exploited?
It is not in CISA's Known Exploited Vulnerabilities catalog, and CISA's SSVC assessment does not mark exploitation as active. That does not mean it has not been attacked: vendors and researchers can report attacks before CISA lists them. No public exploit code is tracked.Source: cve.now feed data
What does this mean?
The login handler mesh_login.cgi does not properly check authentication when the account lookup finds no matching account. The advisory says this lets an unauthenticated user receive a fully privileged admin session, and that this can be chained into unauthenticated remote root command execution.Source: github.com
Which versions are affected by CVE-2026-121615?
E5600: version 1.1.0.26.Source: cve.now feed data
Am I affected, and how do I check?
The affected product is the Linksys E5600 on firmware v1.1.0.26. Compare the firmware version on the device with that version to see whether it matches.Source: github.com
How do I fix CVE-2026-121615?
The checked facts do not name a fixed firmware version, so no upgrade target can be given from them.Source: github.com
What if there's no patch?
The checked facts list no fix and no workaround. The flaw is in the login handler mesh_login.cgi, and the facts offer no narrower step beyond waiting for a firmware update.Source: github.com