VulnerabilityPublished 13 Aug 2026Updated 31 Oct 2026

CVE-2026-30922: S3ql · Denial of Service in pyasn1 via Unbounded Recursion

Affects s3qlSource GCVE Database

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Not known to be exploited · CVSS 7.5 High : upgrade to 3.8.1 soon.

Data as of 1 Nov 2026, 01:50 UTC

CVSS 3.0 base score

7.5High

How severe the flaw is on the 0–10 CVSS scale.

Patch: Available – fixed in 3.8.1

CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Attack Vector: Network
Attack Complexity: Low
Privileges Required: None
User Interaction: None
Scope: Unchanged
Confidentiality: None
Integrity: None
Availability: High

Bold values are the worst case: easiest to exploit or largest impact.

Attack Vector: Network: The vulnerable component is bound to the network stack and the set of possible attackers extends beyond the other options listed, up to and including the entire Internet. Such a vulnerability is often termed 'remotely exploitable' and can be thought of as an attack being exploitable at the protocol level one or more network hops away (e.g., across one or more routers).
Attack Complexity: Low: Specialized access conditions or extenuating circumstances do not exist. An attacker can expect repeatable success against the vulnerable component.
Privileges Required: None: The attacker is unauthorized prior to attack, and therefore does not require any access to settings or files to carry out an attack.
User Interaction: None: The vulnerable system can be exploited without any interaction from any user.
Scope: Unchanged: An exploited vulnerability can only affect resources managed by the same security authority. In this case, the vulnerable component and the impacted component are either the same, or both are managed by the same security authority.
Confidentiality: None: There is no loss of confidentiality within the impacted component.
Integrity: None: There is no loss of integrity within the impacted component.
Availability: High: There is total loss of availability, resulting in the attacker being able to fully deny access to resources in the impacted component; this loss is either sustained (while the attacker continues to deliver the attack) or persistent (the condition persists even after the attack has completed). Alternatively, the attacker has the ability to deny some availability, but the loss of availability presents a direct, serious consequence to the impacted component (e.g., the attacker cannot disrupt existing connections, but can prevent new connections; the attacker can repeatedly exploit a vulnerability that, in each instance of a successful attack, leaks a only small amount of memory, but after repeated exploitation causes a service to become completely unavailable).

Definitions: FIRST CVSS v3.1 specification.

Exploitation evidence

Disclosed: evidence found.
CVE published 13 Aug 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponized: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 31 Oct 2026.

Disclosed: The CVE record is public on cve.org. Its publication is t = 0.
Detectable: A public nuclei template can find exposed instances, for defenders and attackers alike.
Weaponized: A Metasploit exploit module or Exploit-DB entry exists (Metasploit scanner modules do not count), or CISA SSVC or the CVSS exploit maturity reports a public proof of concept.
Exploited in the wild: CISA KEV lists it, CISA SSVC rates exploitation active, or a source reports attacks.
Observed by OffSeq Mirage: OffSeq Mirage honeypot sensors recorded attack traffic for this CVE, or found exposed hosts without attack traffic.

Moments are spaced evenly, not to scale; a dashed line marks a gap of six months or more. Deltas count from t = 0. Sources that give only a date (CISA KEV, Exploit-DB, or a time of exactly 00:00Z) read “same day” rather than hours. Metasploit modules carry the flaw’s disclosure date, not their release date, and nuclei templates carry no date, so both appear above but not on the timeline.

What to do

Upgrade s3ql to 3.8.1.

Patches and advisories

Affected software

Product	Affected	Fixed in
Homebrews3ql`pkg:brew/s3ql`Other threats	Affected >=3.1 <3.8.1	Fixed in 3.8.1

Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.

AI-suggested

A patch is available in pyasn1 version 3.8.1 that addresses this vulnerability by presumably adding recursion depth checks or other controls. Users should upgrade to version 3.8.1 or later to remediate this issue. No additional mitigation is noted in the vendor advisory. Until patched, avoid parsing untrusted ASN.1 data with vulnerable versions.

Description

The pyasn1 library suffers from a Denial of Service vulnerability due to unbounded recursion when decoding ASN.1 data with deeply nested indefinite length SEQUENCE or SET tags. An attacker can craft a payload that causes the decoder to recurse until the Python interpreter crashes with a RecursionError or exhausts memory, crashing the host application. This affects services parsing untrusted ASN.1 data such as LDAP, SNMP, Kerberos, or X.509 parsers. Versions from 3.1 up to but not including 3.8.1 are vulnerable. A fix is available in version 3.8.1.

Impact

Remote attackers can cause a Denial of Service by crashing any service using pyasn1 to parse untrusted ASN.1 data. The crash results from unhandled RecursionError or memory exhaustion. This can terminate worker processes or threads, disrupting service availability. The attack requires a small payload (under 100 KB) but can consume significant RAM or stack space, especially if recursion limits are increased. No confidentiality or integrity impact is reported.

Summary

The vulnerability in pyasn1 arises because the decoder recursively calls itself for every nested ASN.1 component without limiting recursion depth. Specifically, indefinite-length constructed types and standard decoding of SEQUENCE, SET, SEQUENCE OF, and SET OF types invoke recursive decoding without depth checks. This allows an attacker to supply a crafted payload with deeply nested indefinite length tags (0x30 or 0x31 with 0x80 length marker) that triggers unbounded recursion. The recursion leads to a RecursionError or memory exhaustion, causing a Denial of Service by crashing the Python interpreter or consuming all available memory. The vulnerability affects pyasn1 versions >=3.1 and <3.8.1 and is fixed in 3.8.1. The issue was responsibly disclosed and is documented with a proof-of-concept that triggers the crash with a payload under 10 KB.

References

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