ASN1SCC: Stack buffer overflow and out-of-bounds read in XER tokenizer NT()
Affects asn1scc versions before 4.7.0.1 (asn1crt runtime) when parsing XER input with tag names of 100 or more characters or truncated payloads. Fixed in 4.7.0.1.
Written by anthropic/claude-haiku-5.5 from the sources below. Verify against them.
- Exploited
- No known exploitation
- Fix
- Fixed in 4.7.0.1
- Who is exposed
- Not reported
Do first: Upgrade to a fixed version: 4.7.0.1.
- Last modified
- 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? →
- 25/100 · 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 ASN1SCC ASN.1 compiler for embedded systems has a stack buffer overflow and out-of-bounds read in its XER tokenizer, which every XER decode path uses. A remote attacker without logging in can send a crafted XER message to read adjacent memory, corrupt stack data, crash or hang the decoder, and potentially run code.
Read the original description
ASN1SCC is an open source ASN.1 compiler for embedded systems. Prior to 4.7.0.1, the XER tokenizer NT() in asn1crt/asn1crt_encoding_xer.c, which is reached by all XER decode paths, copies tag characters into a fixed char Value[100] field without a length bound and reads input and lookahead bytes without checking the buffer count. A crafted XER message with an overlong tag can overwrite the tokenizer's stack frame, while a truncated tag or unterminated processing-instruction or comment sequence can read beyond the input and may cause a CPU spin. The flaws can disclose adjacent memory, corrupt stack data, crash or hang the decoder, and potentially permit code execution. This issue is fixed in version 4.7.0.1.
cve.now Index
- Exploitation?/40Unknown. No CISA SSVC exploitation rating yet
- Exposure17/25No login or user action needed, reachable over the network without a login · Unknown: Advisories don't say whether default setups are affected
- Reach?/20Unknown. No tracked technology or package matched
- Severity8.1/10CVSS 8.1
- No patch0/5No signal
What would change the score
- Would score about 70 if added to CISA KEV
- Would score about 65 if CISA's SSVC rates exploitation active
- Would score about 30 if advisories confirm default setups are exposed
What to do
Upgrade to a fixed version: 4.7.0.1.
Timeline
- CVE published
- First seen by cve.now
Affected versions
- esa asn1scc
fixed in 4.7.0.1
Evidence 3
- Advisory
- Repository
- Repository
Corrections
None so far.
Something wrong on this page? Report an error. Every fix is listed here.
Questions about CVE-2026-76077
Is CVE-2026-76077 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 XER tokenizer's NT() routine does not check boundaries while scanning certain malformed input, so a crafted XER message can write past a stack buffer or read memory beyond the end of the input. This can corrupt stack memory, read adjacent memory, or crash or hang the decoder.Source: github.com
Which versions are affected by CVE-2026-76077?
asn1scc: before 4.7.0.1.Source: cve.now feed data
Am I affected, and how do I check?
Versions of asn1scc before 4.7.0.1 that use the asn1crt runtime to decode XER are affected. The bug is triggered by an XML tag name of 100 or more characters, a truncated XER payload such as an unclosed tag, or an unterminated processing-instruction or comment sequence. To check a version, look at the asn1scc version reported by your build or package manager.Source: github.com
How do I fix CVE-2026-76077?
Upgrade asn1scc to 4.7.0.1 or later, which contains the fix in commit fe6ab763bc60d8a2def4104c15414809b45fffd9.Source: github.com