CyberSecBulletin
CVE-2026-31827NVD status: Deferred

Alienbin: Concurrent Execution using Shared Resource with Improper Synchronization

Published Updated By the CyberSecBulletin desk

CVE-2026-31827 is a high-severity concurrent execution using shared resource with improper synchronization vulnerability in Alienbin from Blue-B, with a CVSS 4.0 base score of 7.1 out of 10. It can be exploited remotely over the network by an attacker with a low-privileged account, without any action from a user. Affected Alienbin versions: <= 1.0.0. The record does not name a fixed version, so check the vendor advisory. There is no confirmed exploitation so far. EPSS estimates a 0.21% chance of exploitation within 30 days, which is low compared with other CVEs.

Next patch cycle

High severity with no evidence of exploitation so far.

What to do

  1. Check which version of Alienbin you run against the affected versions below, and install the vendor's latest release.
  2. Read the advisory on github.com for workarounds and exact fixed builds.

Affected products and versions

VendorProductAffected versionsFixed in
Blue-BAlienbin<= 1.0.0Not stated

Version data comes from the organisation that assigned the CVE. Confirm against the vendor advisory before deciding you are unaffected.

How the severity score breaks down

Attack vector
NetworkCan be exploited remotely over a network, including the internet.
Attack complexity
LowNo special conditions are needed; the attack works reliably.
Attack requirements
NoneThe attack does not depend on a particular deployment or configuration.
Privileges required
LowA basic user account is enough.
User interaction
NoneNo action by a victim is required.
Confidentiality (vulnerable system)
NoneNo loss of confidentiality on the vulnerable system.
Integrity (vulnerable system)
NoneNo loss of integrity on the vulnerable system.
Availability (vulnerable system)
HighSerious loss of availability on the vulnerable system.
Confidentiality (other systems)
NoneNo loss of confidentiality on systems beyond the vulnerable one.
Integrity (other systems)
NoneNo loss of integrity on systems beyond the vulnerable one.
Availability (other systems)
NoneNo loss of availability on systems beyond the vulnerable one.

Vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X. Scored by CNA (github.com).

Official description

Alienbin is an anonymous code and text sharing web service. In 1.0.0 and earlier, the /save endpoint in server.js drops and recreates the MongoDB TTL index on the entire post collection for every new paste submission. When User B submits a paste with a short TTL (e.g., 30 seconds), the TTL index is recreated with expireAfterSeconds: 30 for all documents in the collection. This causes User A's paste (originally set to 7 days) to be deleted after 30 seconds. An attacker can intentionally delete all existing pastes by repeatedly submitting pastes with ttlOption=30s.

Source: the CVE record as published by its numbering authority, via NVD and CVE.org.

The underlying weakness: Concurrent Execution using Shared Resource with Improper Synchronization

The product contains a concurrent code sequence that requires temporary, exclusive access to a shared resource, but a timing window exists in which the shared resource can be modified by another code sequence operating concurrently.

How developers prevent this class of flaw

  • In languages that support it, use synchronization primitives. Only wrap these around critical code to minimize the impact on performance.
  • Use thread-safe capabilities such as the data access abstraction in Spring.
  • Minimize the usage of shared resources in order to remove as much complexity as possible from the control flow and to reduce the likelihood of unexpected conditions occurring. Additionally, this will minimize the amount of synchronization necessary and may even help to reduce the likelihood of a denial of service where an attacker may be able to repeatedly trigger a critical section (CWE-400).

More Concurrent Execution using Shared Resource with Improper Synchronization vulnerabilities (CWE-362)

Timeline

  1. CVE record published.
  2. CISA published its SSVC assessment (exploitation: none, automatable: no, technical impact: partial).
  3. Record last changed materially (score, affected products, status or references).

References

Recent Concurrent Execution using Shared Resource with Improper Synchronization vulnerabilities

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