TOTOLINK A950RG Basic Wireless Configuration cstecgi.cgi strcpy stack-based overflow
Written by anthropic/claude-haiku-5.5 from the sources below. Verify against them.
- Exploited
- Proof of concept public, per CISA
- Fix
- No fix listed
- Who is exposed
- Specific setups only
Do first: Check whether your setup matches what the bug needs. Firmware TOTOLINK A950RG V4.1.2cu.5268_B20221104 The addEffect parameter must be non-zero to enter the block containing the copy keyFormat must be a value other than 1 so the strcpy branch is taken
- Exploitation15/40CISA rates a proof of concept as public
- Exposure8/25Specific setups only, reachable over the network
- Reach?/20Reach: unknown (data gap). No tracked technology or package matched
- Severity10/10CVSS 9.4, total technical impact per CISA
- No patch5/5No patch listed yet
What would change the score
- Would score about 73 if added to CISA KEV
- Would score about 68 if CISA's SSVC rates exploitation active
- Would score about 45 if CISA's SSVC rates it automatable
CVE-2026-121598 is not in CISA's Known Exploited Vulnerabilities (KEV) catalog. No public exploit code is tracked. It is rated CVSS 9.4 (critical) and affects A950RG; 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- Where the record stands: published, rejected by its publisher, or superseded by another id.What do these mean?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? →
- 0.47% · 40th 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? →
- 38/100 · 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? →
- Specific setups only
- 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
- Exploitation: poc
- Automatable: no
- Technical impact: total
Summary
The TOTOLINK A950RG wireless router firmware, specifically its Basic Wireless Configuration handler in the cstecgi.cgi web interface, is affected. A remote attacker could exploit a stack-based buffer overflow through the wepkey parameter, potentially crashing the device or running arbitrary code on it.
Read the original description
A security vulnerability has been detected in TOTOLINK A950RG 4.1.2cu.5268_B20221104. This impacts the function strcpy of the file /cgi-bin/cstecgi.cgi of the component Basic Wireless Configuration Handler. The manipulation of the argument wepkey leads to stack-based buffer overflow. It is possible to initiate the attack remotely. The exploit has been disclosed publicly and may be used.
What to do
Check whether your setup matches what the bug needs.
Firmware TOTOLINK A950RG V4.1.2cu.5268_B20221104 The addEffect parameter must be non-zero to enter the block containing the copy keyFormat must be a value other than 1 so the strcpy branch is takenWorkaround: The checked facts give no workaround. The advisory's conditions point to addEffect and keyFormat, but the facts do not say whether changing those settings removes the risk.
Timeline
- CVE published
- First seen by cve.now
- Posted on X by cve.now
- CISA SSVC assessment
Exploitation: poc · Automatable: no · Technical impact: total
- Record last updated
Affected versions
- TOTOLINK A950RG
4.1.2cu.5268_B20221104
Evidence 6
- Advisory
- Advisory
- Advisory
- Advisory
- Exploit
- Link
Corrections
None so far.
Something wrong on this page? Report an error. Every fix is listed here.
Questions about CVE-2026-121598
Is CVE-2026-121598 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. CISA's SSVC assessment notes a proof of concept exists. No public exploit code is tracked.Source: cve.now feed data
What does this mean?
The setWiFiBasicConfig handler in cstecgi.cgi copies the wepkey value into a stack buffer with strcpy. A wepkey of 113 bytes or more overwrites the saved return address and can crash the CGI process with SIGSEGV. The write-up describes a ROP chain that could let an attacker control execution.Source: gist.github.com
Which versions are affected by CVE-2026-121598?
A950RG: version 4.1.2cu.5268_B20221104.Source: cve.now feed data
Am I affected, and how do I check?
The checked facts list TOTOLINK A950RG firmware V4.1.2cu.5268_B20221104. The copy is reached only when addEffect is non-zero and keyFormat is a value other than 1. Compare your firmware version with that build and check those two settings.Source: gist.github.com
How do I fix CVE-2026-121598?
The checked facts do not name a fixed firmware version, so no upgrade target can be given. Check TOTOLINK's site for a newer A950RG release and apply it when one is published.Source: gist.github.com
What if there's no patch?
The checked facts give no workaround. The advisory's conditions point to addEffect and keyFormat, but the facts do not say whether changing those settings removes the risk.Source: gist.github.com